[R] precision warning in delaunayn function

Jean-Luc Dupouey dupouey at nancy.inra.fr
Thu Jul 26 09:26:12 CEST 2012

Dear R helpers,

I try to use the 'delaunayn' function in the 'geometry' package for 
Delaunay triangulation in 2 dimensions.

For the four following points, I get a warning message :

 > coord=matrix(ncol=2,byrow=TRUE,c(622633,7073452,
+                                  621228,7073517,
+                                  621879,7071762,
+                                  621065,7073331))
 > library(geometry)
 > test=delaunayn(coord,options="Qbb")

qhull precision warning:

The initial hull is narrow (cosine of min. angle is 0.9999999999999999).
Is the input lower dimensional (e.g., on a plane in 3-d)?  Qhull may
produce a wide facet.  Options 'QbB' (scale to unit box) or 'Qbb' (scale
last coordinate) may remove this warning.  Use 'Pp' to skip this 
warning. See 'Limitations' in qh-impre.htm.

I read carefully qh-impre.htm and I still do not understand why I get 
this message.  A simple call to plot(coord) shows that the points are 
not aligned, nor very close.

What did I miss?

Thanking you in advance,

Jean-Luc Dupouey
INRA-Lorrain University
Forest Ecology & Ecophysiology Unit
F-54280 Champenoux
mail: dupouey at nancy.inra.fr

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